Conventionally, a wiper apparatus is mounted on a vehicle such as automotive vehicle, and configured to wipe off foreign objects such as rainwater and dust on a windshield. The wiper apparatus is provided with: wiper members provided on the windshield; and a wiper motor configured to swing the wiper members. By switching on a wiper switch provided in an interior of the vehicle, the wiper motor is rotated, thereby swinging the wiper members on the windshield. Since the wiper motor is installed in a small space of this vehicle, a motor with speed reduction mechanism is employed to secure a reduced size and a large output power.
Such a motor with speed reduction mechanism is provided by, for example, a technique described in Japanese Unexamined Patent Application Publication No. 2002-147575 (FIGS. 2 and 5). The motor with speed reduction mechanism described in Japanese Unexamined Patent Application Publication No. 2002-147575 (FIGS. 2 and 5) has a worm to be rotated by the motor, and a worm wheel engaged with the worm. The worm and the worm wheel make up the speed reduction mechanism. This worm speed reducer can be adopted in many cases as in-vehicle motor with speed reduction mechanism. The motor rotates the worm with a small diameter at high speed, which in turn rotates the worm wheel with a large diameter at low speed. The worm wheel thus outputs a high torque.
In order to allow the speed reduction mechanism to operate smoothly for a long period, a predetermined amount of grease (highly viscous lubricating oil) is applied to a mating part where the worm and the worm wheel are in engagement with each other. Although grease is highly viscous, grease is movable to both sides of the worm in its longitudinal direction to end up in gathering in a one-sided location, or scattered to surroundings of the worm by rotation of the worm. This leads to exhaustion of grease on the mating part. In order to prevent one-sided displacement of greases, according to the technique described in Japanese Unexamined Patent Application Publication No. 2002-147575 (FIGS. 2 and 5), a guide member which guides grease toward the center of the worm in its axial direction is disposed on both sides of the worm in its axial direction. On the other hand, in order to prevent grease from being scattered by rotation of the worm, a housing is brought closer to the worm.